1. Field of the Invention
The invention relates to an electronic equipment such as a car audio and, in particular, to an electronic equipment including an operation tool structured such that it can be crashed against an impact.
2. Description of the Related Art
In order to enhance the safety of an occupant in a vehicle collision, there is a requirement for safety in an apparatus such as an audio to be incorporated into an instrument panel within a vehicle room. For example, in Europe, assuming that an occupant can collide with an operation tool such as a knob in a vehicle collision, there is established a standard that the operation tool such as a knob must be dented when a certain impact load is applied thereto. In order to be able to meet such standard, conventionally, the operation tool is structured such that it can be crashed against an impact to thereby reduce the degree of the projection of the operation tool from the front surface of the electronic equipment in which the operation tool is incorporated (For example, the patent reference 1: JP-A-2001-266704 (Page 3, FIGS. 1, 2)).
Here, FIGS. 8A and 8B show an example of an operation tool in a related art. An operation tool 100 is a volume knob of a car audio and is supported by an encoder 102 which is used to detect the angle of the knob. FIG. 8A shows the operation tool 100 in its normal state and FIG. 8B shows the operation tool 100 when it is crashed.
The operation tool 100 is composed of an outer knob 104 and an inner knob 106 which are both made of resin. The outer knob 104 has a cylindrical shape, while it can be picked up and rotated by an operator. The inner knob 106 is fitted with the inside of the outer knob 104. And, the inner knob 106 includes a mounting portion 108 to be mounted on the encoder 102.
The mounting portion 108 has a tube portion 110 which can be fitted with the outside of the encoder 102. The tube portion 110 has an engaging projection 111 for prevention of removal, while the engaging projection 111 can be engaged with the encoder 102.
Also, the tube portion 110 includes, on its inner surface, two crashable projections 112, 114. The crashable projections 112, 114 are disposed at positions which correspond to the stepped end faces 116, 118 of the encoder 102, while they can be contacted with these end faces 116, 118.
As shown in FIG. 8B, when the body of the occupant collides with the operation tool 100 in a vehicle collision, an impact force acts in the arrow mark (in FIG. 8B) direction and, due to the impact force, the crashable projections 112, 114 are bent, thereby removing a restraint on the movement of the mounting portion 108 toward the encoder 102. Accordingly, the operation tool 100 is allowed to move toward the encoder 102 and thus the operation tool 100 is dented, thereby satisfying the requirement for the collision safety of the occupant.
However, in the case of the conventional operation tool 100 shown in FIG. 8, since the two crashable projections 112, 114 are disposed on the mounting portion 108 and thus there are provided the mounting function and the crashing function in the same portion, there is a possibility that the two functions are not easy to coexist with each other. The crashing function means a function by which, in a collision, the operation tool can be crashed and the projection of the operation tool can be thereby reduced as required. On the other hand, the mounting function means a function by which the operation tool can be supported positively, that is, the shaking motion of the operation tool can be controlled within the required range.
Here, describing the above problem further with reference to FIGS. 8A and 8B further, in a vehicle collision, the crashable projections 112, 114 are broken in the mounting portion 108 to thereby remove the mounting of the mounting portion 108 with respect to the encoder 102, so that the mounting portion 108 moves toward the encoder 102 and the whole of the operation tool 100 also moves toward the encoder 102. That is, to secure the crashing function, removal of the mounting of the mounting portion 108 due to the crash of the crashable projections 112, 114 is necessary, which limits the strength of this mounting portion 108. Accordingly, there is a limit on the reinforcement of the mounting portion 108 from the viewpoint of prevention of the shaking motion of the operation tool.
Also, according to the structure shown in FIGS. 8A and 8B, when the mounting portion 108 advances toward the encoder 102, the tube portion 110 advances while spreading in a trumpet manner. In case where the tube portion 110 does not cause such trumpet-like spreading deformation, the tube portion 110 will be butted against the encoder 102. Therefore, to secure the crashing function, the tube portion 110 must be weak to such a degree that the above-mentioned spreading deformation is possible. Specifically, the thickness of the tube portion 110 is limited. Therefore, there is a limit on the enhancement in the rigidity of the tube portion 110 from the viewpoint of prevention of the shaking motion.
In this manner, in the conventional structure, the mounting and crashing portions are formed integral with each other, whereas the requirements for the mounting and crashing functions do not agree with each other. And, there exists a trade-off relationship that, in case where one of the two functions is enhanced, the other function is degraded. This means that, in some cases, the two functions are difficult to be compatible. Also, in case where much importance is attached to the crashing function for enhancement in the occupant safety, it is difficult to enhance the mounting function, so that it is sometimes not easy to reduce the shaking feeling of the operation tool.